From 6644736533985058275 X-Google-Thread: f78e5,e4aa14519cca09ff X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII Path: g2news1.google.com!news4.google.com!newsfeed2.dallas1.level3.net!news.level3.com!newsfeed-00.mathworks.com!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: kon@iki.fi (Kalle Olavi Niemitalo) Newsgroups: comp.std.c++ Subject: Re: My nitpicks on n1774 Date: Mon, 2 May 2005 19:59:24 GMT Organization: Oulun Puhelin Oyj - Baana Lines: 110 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: <87vf63z31d.fsf@Astalo.kon.iki.fi> References: <1gvl3nc.1btw8bq15u28exN%thedl0-usenet1@yahoo.com> <1114785595.237226.56270@g14g2000cwa.googlegroups.com> NNTP-Posting-Host: news.news.demon.net Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: quoted-printable X-Trace: news.demon.co.uk 1115063970 13853 158.152.254.254 (2 May 2005 19:59:30 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Mon, 2 May 2005 19:59:30 +0000 (UTC) X-OPOY-MailScanner-SpamCheck: not spam, SpamAssassin (score=1.389, required 5, AWL -0.41, BAYES_50 0.00, UNWANTED_LANGUAGE_BODY 1.80) X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-User-Agent: Gnus/5.110003 (No Gnus v0.3) Emacs/22.0.50 (gnu/linux) X-OPOY-MailScanner-Information: Please contact the OPOY for more information X-Virus-Scanned: by amavisd-new at cs.mu.OZ.AU X-OPOY-MailScanner-SpamScore: s X-Cancel-Lock: sha1:HpNIBs6A0s6NPnrCkfP/57sjS6g= X-Path: comp-std-cpp-robomod!not-for-mail X-Received: (from fjh@localhost) by mulga.cs.mu.OZ.AU (8.12.10+Sun/8.12.9/Submit) id j42JxOjc020502; Tue, 3 May 2005 05:59:24 +1000 (EST) X-OPOY-MailScanner: Not virus scanned: please contact OPOY for details X-NNTP-posting-date: Sun, 1 May 2005 09:56:03 +0000 (UTC) X-Delivered-To: std-c++@ucar.edu X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-MailScanner-From: news@plaza.suomi.net X-MIME-Autoconverted: from 8bit to quoted-printable by mulga.cs.mu.OZ.AU id j42JxRHb020531 X-Accept-Language: fi;q=1.0, en;q=0.9, sv;q=0.5, de;q=0.1 X-Keywords: std::integer,exception safety,negative zero,Common Lisp, std::iostream,std::locale::num_put X-Newsgroups: comp.std.c++ Xref: g2news1.google.com comp.std.c++:4659 "msalters" writes: > What's small? I'd say that if the memory allocation fails, the result > is /by definition/ not small - even if it's just 4 bytes. I think it is quite odd to throw an overflow_error from a copy constructor; if the value was OK for one instance of the class, then it should also fit in others. Also, I think it will be easier to recover from the exception (e.g. retry with a different algorithm that allocates less memory) if it is a bad_alloc rather than overflow_error. Or define a new exception class derived from both? If an exception occurs in a non-const member function, does the integer object retain its previous value? [lib.integer.members] #10: Does the constructor also throw if the string contains no digits, or if the string contains '+' or '-' anywhere except at the beginning? [lib.integer.members] #8-#12: There could also be a constructor that takes a range of chars delimited by two bidirectional iterators. Perhaps even remove the conversion from std::string altogether. integer(char const*) should still be kept because it is so convenient with string literals. [lib.integer.members] #8-#12: The constructor could take the numeric base as another parameter (int base =3D 10). When the base is a power of 2, the complexity can be O(N) in typical implementations. I think it'd be better not to add a constructor integer(char const*, int base), because it'd be too easy to assume the second parameter is the length of the string. Possibly allow base=3D=3D0 with the same meaning as in strtol. [lib.integer.members] #16: The complexity of the copy assignment operator seems too high; I'd expect O(N). (First noted by Daniel Kr=FCgler: Is N the number of bits in the new value, or the sum or maximum of bits in both values?) [lib.integer.members] #20: Likewise, the assignment from long long should perhaps be O(1) like the corresponding constructor. [lib.integer.members] #25: Preventing out_of_range also requires a comparison to integer(LONGLONG_MIN). [lib.integer.members] #26: I dislike the use of "hex" to mean base 16 rather than 6, even though iostreams already do this. The specification could at least say "number of hexadecimal digits". [lib.integer.member.arithops] #3, #9: Again, what is the N in O(N)? [lib.integer.member.arithops] #12: I think -=3D and +=3D should have the same complexity. [lib.integer.member.arithops] #22, #25, #29: How do *=3D and /=3D round or truncate the result? [lib.integer.member.bitops]: I'd like to note that Common Lisp has arbitrary-size integers and specifies that bitwise and shift operations must treat them as binary two's complement. (The representation in memory is unspecified.) This means it can have the equivalent of operator ~ without inconsistencies. [lib.integer.iostream]: > "Various applicable formatting state" is something I'm not > entirely certain about. - boolalpha: no effect (not bool). - dec, hex, oct, showbase: would go along nicely with the base parameter to the constructor. - fixed, scientific, showpoint, precision: no effect (not floating point). - left, internal, right, width: can't be that hard to implement. - showpos, uppercase, skipws: easy! - unitbuf: I'm not sure but it looks like this is automatic if you don't access the streambuf directly. - exceptions: Apparently involves catching the overflow_error (or bad_alloc) from internal calculations and setting badbit. - imbue: I think this would require extending std::locale::num_put or defining an entirely new facet. Anything else? [lib.integer.member.comp] #1: Because the bitwise member operators do not change the sign, it seems possible to generate a negative zero. The current wording for operator =3D=3D makes the negative zero compare not equal to a positive zero ("sign" is not written in the font used for identifiers), with a nasty effect on operator /=3D. [lib.integer.funs] #2: Should be "returns false if abs(v) < (integer(1)<